Compressor blading



J y 1965 J. R. ERWIN ETAL 3, 85

COMPRESSOR BLADING Filed 001:. 29, 1962 INVENTOR5. J0/l/V e. few/1v By wear/r. alum: ./e.

rew A nrramvey- United States Patent 3,193,185 COMPRESSOR BLADING John R. Erwin and Leroy H. Smith, Jr., Cincinnati, Ohio, 'assignors to General Electric Company, a corporation of New York Filed Oct. 29, 1962, Ser. No. 233,661

Claims. (Cl. 230-120) The present invention relates to blading and, more particularly, to compressor blading that has flow augmenting means as an integral part thereof.

One of the problems encountered in axial flow compressors of the types commonly used in jet engines is that of compressor stall. The causes of and theories surrounding compressor stall are not completely understood but can be conveniently summarized by stating that the compressor blading is unable to provide the pressure rise which is required for smooth operation. In other words, the airflow through the compressor is disturbed resulting in pressure pulses and stall of the airflow through the compressor. This can be quite serious in a reaction powerplant since it chokes off operation of the powerplant. Many devices and schemes have been employed to either stop compressor stall or to detect it early enough so that remedial steps may be taken. Other solutions have attempted to put the stall outside the operating range of the powerplant where it is then of no concern. The instant invention is a means of achieving this last solution. The phenomenon of boundary layer is well known and is found in compressor and turbine operation. While applicable to a turbine, the invention is primarily suited for but not limited to compressors and will bedescribed in connection with compressors. In a typical compressor where wall members are formed by a casing and hub respectively with airfoil blades operating in an annulus between the walls, it is known that boundary layer air tends to adhere to the adjacent Walls. This results in slow moving low energy air at these walls and a tendency to break down the smooth primary airflow to the blades.

The main object of the present invention is to provide compressor blading employing means to relocate and/ or energize the boundary layer air.

Another object is to provide such blading with an attachment that enables the secondary fiow to be augmented for moving the boundary layer for better mixing and also assist in turning the fluid in the direction resulting in greater energy addition to the low energy boundary layer fluid.

A further object is to provide a compressor rotor having blading which, by means of an attachment thereto, promotes mixing and turning of the low energy boundary layer and consequent postponement of compressor stall.

Briefly stated, the present invention includes a compressor rotor with a hub to form an inner wall member and an outer casing to form an outer wall member with a row of cambered airfoil blades attached to one of the walls and radially extending towards the other wall. An axially-extending air passage is thus formed containing the blades for passage of air therethrough. The blades are equipped with flow directing vane-like means mounted substantially at right angles to each blade and located adjacent one of the Walls." The vane-like means is oriented on the blades so that the flow passing across the concave pressure surface of the blade is directed by the vane-like means toward the adjacent wall.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed the invention will be better understood from the following 3,193,185 Patented July 6, 1965 description taken in connection with the accompanying drawing in which:

FIGURE 1 is a partial diagrammatic cross-section of a compressor rotor,

FIGURE 2 is a partial view of a pair of rotor blades illustrating the cross-flow between the blades,

FIGURE 3 is a top view taken on the line 33 of FIGURE 2,

FIGURE 4 is a view similar to FIGURE 2 showing the addition of the vane-like means adjacent the hub,

FIGURE 5 is a similar view showing a diflerent vanelike means adjacent the hub and the tip of the blade and applied to one side only,

FIGURE 6 is a partial view of a modification using the vane-like means between the blades, and

FIGURE 7 is a plot showing the effect of the vanelike means on the stall characteristics of a typical compressor.

Referring first to FIGURE 1, there is shown diagrammatically a compressor rotor having a hub 10 and an outer casing 11. Both of these form inner and outer wall members respectively. Between these, in the conventional manner, the hub 10 carries rows of rotor blades 12 and casing 11 has similar stator blades 13 each extending radially toward the opposite wall. An axially-extending air passage 14 is thus formed in the conventional manner for the flow of air through the compressor to emerge at higher pressure on the right end of the figure.

Reference to FIGURE 2 showing a pair of rotor blades will illustrate the flow difficulties encountered in a compressor. It should be understood that the discussion of the invention will proceed with respect to the rotor blades for convenience only and that the same reasoning applies to the stator blades. Since the rotor blades are conventionally cambered airfoils having convex pressure and concave suction surfaces as shown in FIGURE 3, there are two airilows that normally occur. The first is the primary airflow which approaches the leading edge of the blades and exits from the trailing edge as shown by the straight arrow in FIGURE 3 and is compressed to a higher pressure in the usual manner. The second flow is called secondary flow and is the motion of the air essentially normal to the main flow or transverse of the passage. This secondary fiow comes about due to the pressure fields that exist in the blades and due to the low momentum level of the boundary layer fluid. As shown in FIGURES 2 and 3, the convex blade surface is normally at a lower pressure, as indicated by the minus sign, than the concave surface. The concave surface is at a higher pressure indicated by the plus sign in both figures. Because of this pressure diiference acting along "the boundaries of the walls of the passage, it can be seen that a secondary flow occurs transversely within the passage between adjacent blades and this flow passes from the higher to the lower pressure region as shown by the curved arrows in FIGURES 2 and 3. This occurs near the walls 10 and 11. It can be seen then that the secondary flow, as shown by the curved arrows in FIGURE 3, has a significant transverse or cross-passage component whereas the deflection of the main stream of air caused by the blading does not have such a large component. This greater cross-passage or transverse component results in a larger turning and therefore an increased energy addition to the low momentum boundary layer fluid.

The secondary flow, when viewed in the projection of FIGURE 2, is shown by arrows 15. Thus, the secondary flow transports main stream fluid along the concave surface of the blade toward hub 10 and casing 11 within the air passage as shown by the arrows and transports the boundary layer fluid away from the hub and casing into the center portion of the axial passage between adjacent blades along the convex blade surface. This results in mixing of the. flows. The result of both the turning and mixing is that the boundary layers are energizedso that a.higher pressure rise across the compressor blading may be accomplished-without; stall.

The instant inventionis intended tolaugmentv the turnboundary layer, the term adjacent wall is intended to be that wallon which the nearest-boundary layer isfound.

ing as well as promote the mixing of the boundary layer into the main air stream. By thus augmenting and mix- 7 ing, it is possibleto obtain higher pressure rise per compressor stage resultingin compressors with fewer stages for a given compression ratio.

In order to augment the turning and like means 16 as shownjin FIGURE.4 These vane-like means 16, which may be flat (i.e., zero camber) but are preferably more cambered as shown, are particularly located at rightangles to the blade, whether stator or rotor, so that the main flow pas'sing near the concave promote the mixing the airfoils are provided with flow directing vane- Referring next to FIGURE 6,- a modification is shown I wherein the vane-like means 21 may be attached to the 5 air particle on the concave or plus side of blade 12 would follow the 'path shown by arrow and line 22 as it migrated along the hub toward adjacent blade 12. With vane 12 in place and oriented as shown, the same particle'follows the surface of the blade is directed toward the adjacent wall.

As applied to FIGURE 4, blade 12has a concave surface 17 and a convex surface 18. Since-the main airstreami flow shown by arrow 19 creates-the secondary flow shown in FIGURE 2, due to the blade pressure surfaces,

the vane means 16is oriented and cambered on the blade 12 to direct the flow down as shown in FIGURE 4 on the i concave surface across the passage between the bladesand up or radially out as shown on the convex surface" of the adjacent upstream blade; Thus, vane-means 16 is oriented substantially at right angles on blade '12 to pro-j mote flow in this direction. Sincethe natural secondary flow: occurs in this directioi'uflthe vane-like membersgreatly augment this fiow but caneven reverse the flow if the naturalsecondary fiow is reversed, Furthermore, since the-low momentum fluid is actually the boundary layer fluid, the vanes are disposed at a radial location along blade 12 substantially at the surface of the boundary layer of the adjacent wall and-thus adjacent the wall. In FIGURE 4 this locates vane 16 at the surface of the boundary layer on wall or hub 10. This is the root portion of rotor blade 12 as shown in FIGURE 4. Sim

ilarly, it'is possible that the vane-like'means 16 may be required on the tip portion of the rotor blade as well.

This configuration is shown in FIGURE ,5 wherein an additional vane 20 is provided at the tip of the rotor blade near casing '11. 'T he stall characteristics of the particular rotor blade. It may be unnecessary to provide the vanelike means on both sides of the rotor blade. Additionally, various configurations may be provided. As illustrative, the configuration shown in FIGURE 4 is 'a cambered vane means that extends forward of the leading edge of the blade and the configuration of FIGURE 5 is a cambered arrangement with the vane means extending substantially from the leading edge to thetrailing edge only. This latter permits use in multiplestage com-- pressors without interference. Under-any circumstances, the vane-like means is provided on the concave surface to promote and augment the transverse flow between adjacent blades from the higher pressure concave "surface a to the adjacent upstream blades lower pressure convex suction surface.

The vane means may be applied at both the root and tip portions," as shown in FIGURE 5, to directthe'fiowl Since toward the adjacent wall having a boundary-layer. the vane is disposed substantially at-the surfacefof the In other words, the vanes are oriented to augment. the transverse flow. Additionally, FIGURES illustrates the use of the vane-like means on only one side of the 1 of the vanerlike means permits the stall point of a given path of arrow and line 23 by first: followingthe convex negativeor suctionsurface of vane 21 and onto the convex or suction surface of vane 12. Greater turning is imparted to the particle resulting inmore. energy addition I to the low energy boundary layer, better mixing and augmentation of the secondary transverse flow.

FIGURE 7 illustrates'the results of employing the vane-like means wherein it can be seen thatas'the percentage of vanes is increased, a higher pressure rise is obtainable before stall occurs. In other words, the use compressor to be moved beyond the, operating range. The use of the vane means changes the conventional pressure profile andbringsin greater velocity gradients totransfer energy more rapidly-from the'mainstream 'to they boundary layer by moving the boundary layer transverselyand promotingmixing and energizing re-' sultingin" a greater pressure rise per compressor stage. While. the vane-like.,.means have been shown as curved or cambered in FIGURE 4 and substantially fiat or near zero camber in FIGURE 5, 'it' is preferable that a more {cambered version be used since it provides a stronger V in light of the above teachings.

understood that within the scope of the appended claims,

action with lower losses although it is not absolutely necessary; Furthermore, it is desirable that the vanelike means he applied at least on the concave surface .of the blade, as shown inFIGURE 5, to obtain the desired results. V I

7 While there have hereinbefore been described preferred form s of the invention, obviously many modifications and variations of the present invention are possible It'is therefore to be the invention maybe, practiced otherwise than'as specifically described. v I

'We claim: V V

.1. A rotor having a hub formingan inner wall member,

a casing forming an outer wall member, 7

a row of cambered airfoil blade members having convex suction: and concave pressure surfaces and being attached to one of said wall members and extending radially toward the other wall member to form an axially-extending air passage'through said blades whereby a transverse secondary flow from said pres? sure surface of each blade to said suction surface of the adjacent upstream blade is set up across the air passage between said blades, and flow directing vane-like means on at least one of said members extending into said air, passage and oriented and cambered so that theflow passing near the concave pressure surface ofsaid bladetmembers .is directed by said vane-like means toward the con-- a row' of cambered airfoil blades havingconvex suc-' tion and concave pressure surfaces and beingattached to one of said wall members and extending radially toward the other wall member to form an axiallyextending air passage through said blades, whereby a transverse secondary fiow from said pressure surface of each blade to said suction surface of the adjacent upstream blade is set up across the air passage between said blades,

and flow-directing vane-like means on, and substantially at right angles to, said blades and adjacent at least one of said walls,

said vane-like means being oriented and cambered on said blades so that the flow passing near the concave pressure surface of said blade is directed by said vane-like means toward the adjacent wall and convex suction surface of the adjacent upstream blade.

3. Apparatus as described in claim 2 wherein the vanelike means is radially disposed on said blades substantial ly at the surface of the boundary layer of the adjacent Wall.

4. Apparatus as described in claim 2 wherein the vanelike means is disposed in the root portion of the rotor blades of said compressor rotor.

5. Apparatus as described in claim 2 wherein the vanelike means is disposed at both the root and tip portions of the rotor blades to direct flow near the concave side generally inward at the root portion and outward at the tip portion of said blade.

6. A compressor rotor having a hub forming an inner well member,

a casing forming an outer wall member,

a row of cambered airfoil blades having convex suc tion and concave pressure surfaces and being attached to one of said wall members and extending radially toward the other wall member to form an axially-extending air passage through said blades whereby a transverse secondary flow from said pressure surface of each blade to said suction surface of the adjacent upstream 'blade is set up across the air passage between said blades,

and flow directing vane-like means on, and substantially at right angles to, each of said blades and adjacent at least one of said walls,

said vane-like means extending on said blade from substantially the leading to trailing airfoil edge and being cambered and oriented on said blade so that the flow passing near the concave pressure side of said blade is directed by said vane-like means toward the adjacent wall and convex suction surface of the adjacent upstream blade.

7. Apparatus as described in claim 6 wherein the vanelike means is radially disposed on the leading edge of said blades substantially at the surface of the boundary layer of the adjacent wall.

8. Apparatus as described in claim 7 wherein the vanelike means is disposed in the root portion of the rotor blades of said compressor rotor.

9. Apparatus as described in claim 7 wherein the vanelike means is disposed at both the root and tip portions of the rotor blades to direct flow near the concave side generally inward at the root portion and outward at the tip portion of said blade.

10. Apparatus as described in claim 1 wherein said flow directing vane-like means comprises an airfoil member oriented and overcambered beyond said blade members and radially extending from one of said Wall members between said blade members.

References Cited by the Examiner UNITED STATES PATENTS 566,292 8/96 Bierstadt 25377 571,500 11/96 West 230- 978,677 12/ 10 Taylor 253-77 1,446,011 2/23 Jackson 25377 1,689,383 10/28 Gowdy 25377 1,862,827 6/32 Parsons et al. 23377 2,494,623 1/50 Landt 25377 2,650,752 9/53 Hoadley 230-120 2,844,001 7/58 Alford 230-134 2,920,864 1/60 Lee 230134 3,012,709 12/61 Schnell 230134.2 3,039,736 6/62 Pon 25339 FOREIGN PATENTS 19,441 12/34 Australia. 1,012,041 4/52 France.

611,328 3/35 Germany.

13,234 1890 Great Britain. 26,274 1910 Great Britain. 11,785 1911 Great Britain. 630,747 10/49 Great Britain. 793,143 4/58 Great Britain. 840,543 7/60 Great Britain.

JOSEPH H. BRANSON, JR., Primary Examiner. HENRY F. RADUAZO, Examiner. 

1. A ROTOR HAVING A HUB FORMING AN INNER WALL MEMBER, A CASING FORMING AN OUTER WALL MEMBER, A ROW OF CAMBERED AIRFOIL BLADE MEMBERS HAVING CONVEX SUCTION AND CONCAVE PRESSURE SURFACES AND BEING ATTACHED TO ONE OF SAID WALL MEMBERS AND EXTENDING RADIALLY TOWARD THE OTHER WALL MEMBER TO FORM AN AXIALLY-EXTENDING AIR PASSAGE THROUGH SAID BLADES WHEREBY A TRANSVERSE SECONDARY FLOW FROM SAID PRESSURE SURFACE OF EACH BLADE TO SAID SUCTION SURFACE 